The overall objective of the Technical Core is to develop a range of techniques and instruments and to supply these to the clinical trials, pre-clinical and basic research projects. These include PDT treatment light sources and delivery systems, fiber-optic based in vivo dosimetry devices, assays of photosensitizer concentration in ex vivo human and animal tissue samples, tissue sectioning with standard or special (immuno) histological staining, and optical imaging and image analysis tools. Additionally, it will provide its expertise in these various techniques and technologies techniques as required in each project. A special focus is to help drive the translation of lab-based techniques/technologies and procedures via the pre-clinical studies to the clinical trials. The technical core acts as a central resource for all project leaders and personnel on the program grant. The technical core has the following 5 specific aims: 1. to provide analysis of ex vivo tissue samples for absolute photosensitizer quantification, and (semi) quantitative confocal microscopy to determine extent of necrosis, apoptosis and protein expression in PDT-treated tissues, and primarily provides 'routine' services to the Program, with a limited developmental component. 2. To develop and transfer new treatment and dosimetry procedures to human trials and animal models, including dedicated instrumentation for fluorescence-guided resection, in vivo photosensitizer measurements by diffuse reflectance spectroscopy, multitasking probes, and light sources/delivery systems for acute and metronomic intracranial PDT treatments. This is primarily developmental work. 3. To provide inter-site cross calibrations of light sources and dosimetry instruments and maintain all dosimetric and fluorescence guided resection systems provided to projects 1 and 2, and is a central element of quality assurance across the Program. 4. To develop image analysis techniques for confocal fluorescence microscopy and fluorescence guided resection imaging, and is developmental, but with rapid transfer to the other projects. 5. To fully implement, enhance and maintain the Program Web site which serves the communication between all projects, recruiting efforts of the clinical trials, and information to the general public.